github.com/amarpal/go-tools@v0.0.0-20240422043104-40142f59f616/lintcmd/cache/default.go (about)

     1  // Copyright 2017 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package cache
     6  
     7  import (
     8  	"fmt"
     9  	"log"
    10  	"os"
    11  	"path/filepath"
    12  	"sync"
    13  )
    14  
    15  // Default returns the default cache to use.
    16  func Default() (*Cache, error) {
    17  	defaultOnce.Do(initDefaultCache)
    18  	return defaultCache, defaultDirErr
    19  }
    20  
    21  var (
    22  	defaultOnce  sync.Once
    23  	defaultCache *Cache
    24  )
    25  
    26  // cacheREADME is a message stored in a README in the cache directory.
    27  // Because the cache lives outside the normal Go trees, we leave the
    28  // README as a courtesy to explain where it came from.
    29  const cacheREADME = `This directory holds cached build artifacts from staticcheck.
    30  `
    31  
    32  // initDefaultCache does the work of finding the default cache
    33  // the first time Default is called.
    34  func initDefaultCache() {
    35  	dir := DefaultDir()
    36  	if err := os.MkdirAll(dir, 0777); err != nil {
    37  		log.Fatalf("failed to initialize build cache at %s: %s\n", dir, err)
    38  	}
    39  	if _, err := os.Stat(filepath.Join(dir, "README")); err != nil {
    40  		// Best effort.
    41  		os.WriteFile(filepath.Join(dir, "README"), []byte(cacheREADME), 0666)
    42  	}
    43  
    44  	c, err := Open(dir)
    45  	if err != nil {
    46  		log.Fatalf("failed to initialize build cache at %s: %s\n", dir, err)
    47  	}
    48  	defaultCache = c
    49  }
    50  
    51  var (
    52  	defaultDirOnce sync.Once
    53  	defaultDir     string
    54  	defaultDirErr  error
    55  )
    56  
    57  // DefaultDir returns the effective STATICCHECK_CACHE setting.
    58  func DefaultDir() string {
    59  	// Save the result of the first call to DefaultDir for later use in
    60  	// initDefaultCache. cmd/go/main.go explicitly sets GOCACHE so that
    61  	// subprocesses will inherit it, but that means initDefaultCache can't
    62  	// otherwise distinguish between an explicit "off" and a UserCacheDir error.
    63  
    64  	defaultDirOnce.Do(func() {
    65  		defaultDir = os.Getenv("STATICCHECK_CACHE")
    66  		if filepath.IsAbs(defaultDir) {
    67  			return
    68  		}
    69  		if defaultDir != "" {
    70  			defaultDirErr = fmt.Errorf("STATICCHECK_CACHE is not an absolute path")
    71  			return
    72  		}
    73  
    74  		// Compute default location.
    75  		dir, err := os.UserCacheDir()
    76  		if err != nil {
    77  			defaultDirErr = fmt.Errorf("STATICCHECK_CACHE is not defined and %v", err)
    78  			return
    79  		}
    80  		defaultDir = filepath.Join(dir, "staticcheck")
    81  	})
    82  
    83  	return defaultDir
    84  }